This is a competing continuation application for a Research Scientist Development Award that was received in July 1987. The goal of the proposed research is to improve the treatment of significantly obese women (30 percent or more overweight) by conducting two randomized trials -- one primarily of exercise and the other of diet. Both studies will assess not only changes in weight but also changes in body composition, resting metabolic rate (RMR) and eating behavior, all of which may affect long-term weight control. A third study will examine the effects of weight cycling. The specific aims of each study are: 1) To determine whether resistance/strength training will prevent reductions in fat-free mass and RMR occurring with weight loss and, thus, improve long-term weight control. A total of 128 women will be randomly assigned to four conditions: a) diet alone; b) diet plus aerobic training, c) diet plus strength training; and d) diet combined with aerobic and strength training. Subjects will be treated for 1 year and followed for a second. 2) To assess the effectiveness of portion - and calorie controlled foods in 120 women randomly assigned to three conditions: 1) a 1200 kcal/d liquid diet; 2) a 1200 kcal/d diet of conventional foods; or 3) a 1200 kcal/d mixed diet, consisting of a liquid diet combined with an evening meal of food. The study will examine the hypothesis that liquid diets are initially effective because they facilitate excellent adherence, but are associated with rapid regaining of weight because of subjects' binge eating when they resume consumption of convention foods. This study will provide the first controlled evaluation of a mixed diet that resembles a popular meal-replacement plan and that is expected to capture the benefits of liquid diets while avoiding their drawbacks. 3) To assess the adverse effects of weight loss and regain in 119 women previously treated in our clinic. The candidate wishes to test the hypothesis that weight loss followed by full weight regain is associated with: 1) an increased percentage of body fat; 2) a lower RMR; and 3) increased problem eating (i.e., binge eating). The candidate's scientific development will be facilitated by visits with colleagues who will provide expertise in: 1) strength training and the measurement of energy expenditure during activity; 2) binge eating; 3) measurement of energy expenditure using doubly labeled water; and 4) methodological issues in weight cycling. The proposed research will provide rich training experiences for two postdoctoral fellows, two psychology graduate students, and several psychiatric residents who will collaborate on the studies.